Automatic energy-efficient bathroom exhaust fan controller

ABSTRACT

An automatic control system for an exhaust fan of a room having a water dispensing conduit is disclosed. The system includes a control module that controls delivery of electricity to the exhaust fan to activate and deactivate the exhaust fan, and a sensor suitable for mounting on the water dispensing conduit. The sensor senses temperature of the water dispensing conduit and when a temperature above a predetermined temperature value is reached on the water dispensing conduit, the sensor transmits a control signal to the control module. The temperature increase is due to hot water flowing though the water dispensing conduit (e.g., a shower pipe). Upon receipt of the control signal, the control module activates the exhaust fan for a user selectable time period.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication No. 60/665,650 filed Mar. 25, 2005.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an automatic energy-efficient controller for aroom exhaust fan.

2. Description of the Related Art

Exhaust fans are used to ventilate rooms, such as bathrooms, to preventhumidity from accumulating in the room. Conventional exhaust fans areactivated by a wall switch turned on by the home owner. Many homes donot have electronic or mechanical timers operating the bathroom exhaustfan, and consequently when the fan is turned on, it may remain on for amuch longer time than is necessary to remove the moist air. Thus muchenergy is wasted, as the fan expels air that has been expensively heated(in the winter) or cooled (in the summer).

Consequently, devices have been proposed to automatically controlbathroom exhaust fans. Japanese Patent Application No. JP3286940describes a control device for a bathroom fan where the fan is drivenfor a preset time.

Japanese Patent Application Nos. JP63254339, JP3117838, JP3036445,JP58156134, JP10110982, JP10047719, JP9318111 and JP7120026 describe acontrol device for a bathroom fan where a humidity sensor provides asignal to start and/or stop the fan. In a related application, thedevice of Japanese Patent Application No. JP62194136 uses a humidityreading to determine an operating time for the fan. However, humidistatcontrol tends to be imprecise and slow to respond, and is furthermoreuseless during periods of high humidity in homes that are notair-conditioned.

Japanese Patent Application Nos. JP63254339, JP2003279091 and JP10110982describe a control device for a bathroom fan where a temperature sensorprovides a signal to start and/or stop the fan. However, temperaturecontrol also tends to be imprecise and slow to respond.

Japanese Patent Application No. JP2247436 describes a control device fora bathroom fan in which a hot water feeding switch for a bath alsostarts a ventilating fan. However, this control device appears torequire mounting the control device behind a room wall in line with ahot water pipe.

Japanese Patent Application No. JP2004144383 describes a control devicefor a bathroom fan where a bath water level sensor provides a signal tostart the fan. This device may be slow to respond in that it may take along time before water reaches the sensor level.

Japanese Patent Application Nos. JP1006634, JP9318111 and JP5180475describe a control device for a bathroom fan where a sensor that detectsa person provides a signal to start and/or stop the fan. These devicesmay be inefficient in that fan operation may be triggered when a personenters a room momentarily.

Japanese Patent Application No. JP3236538 describes a control device fora bathroom fan where a light sensor which detects steam provides asignal to start and/or stop the fan. Like a humidity controller for afan, this device may be imprecise and slow to respond.

In view of the disadvantages of known automatic controllers for abathroom exhaust fan, there exists a need for an improved automaticenergy-efficient bathroom exhaust fan controller.

SUMMARY OF THE INVENTION

The present invention provides an automatic energy-efficient controllerfor a room exhaust fan. The invention turns on a bathroom exhaust fanautomatically when someone takes a shower. A thumb-sized smart sensor,clipped onto the shower pipe adjacent to the shower head, detects thetemperature increase when the hot-water valve is opened. The sensor thencommunicates wirelessly with a controller module built into the fan'swall-mounted switch, turning the fan on for a user-selectable timeinterval. A timer permits the homeowner to select the time delay. Thesmart sensor could also be clipped onto the bathtub faucet. Theinvention can be installed easily by a homeowner, and is attractive tobusinesses participating in the burgeoning home-automation retailmarket.

Thus, the invention provides an automatic control system for an exhaustfan of a room having a water dispensing conduit. The system includes acontrol module that controls delivery of electricity to the exhaust fanto activate and deactivate the exhaust fan, and a sensor suitable formounting on the water dispensing conduit wherein the sensor sensestemperature of the water dispensing conduit and the sensor transmits acontrol signal to the control module when a temperature above apredetermined temperature value is reached on the water dispensingconduit. Upon receipt of the control signal, the control moduleactivates the exhaust fan. The control signal may be a radio frequencysignal.

In one version of the invention, the control module activates theexhaust fan by providing electricity to the fan. The control module mayinclude a timer circuit that provides electricity to the fan for apredetermined time period after which the fan is deactivated, and thepredetermined time period may be a variable time period selectable by auser. The control module may include a control for setting thepredetermined temperature value.

In another version of the invention, the control module includes a timercircuit that provides electricity to the fan for a predetermined timeperiod after temperature falls below the predetermined temperaturevalue. The predetermined time period may be a variable time periodselectable by a user.

In one use of the invention, the water dispensing conduit is a showerpipe. In another use, the water dispensing conduit is a bathtub spigot.

It is an advantage of the present invention that the user does not haveto remember to turn on a bathroom exhaust fan. Yet moist air is reliablyremoved from the bathroom, where it otherwise could promote mold growthor accumulate in exterior wall insulation, possibly damaging the house.

These and other features, aspects, and advantages of the presentinvention will become better understood upon consideration of thefollowing detailed description, drawing and appended claims.

DESCRIPTION OF THE DRAWING

FIG. 1 shows an elevational view of a wall of a bathroom including anautomatic energy-efficient controller and an exhaust fan according tothe invention.

DESCRIPTION OF THE INVENTION

Looking at FIG. 1, there is shown a bathroom 10 having a side wall 12and a ceiling 14. Mounted in the ceiling 14 is an exhaust fan 20 thatexhausts air from the interior of the bathroom 10 and out a conduit 22to the attic or outside atmosphere through the roof. A wall mountedmodule 30 communicates via electrical line 32 with the exhaust fan 20 toprovide electricity to the fan 20 to operate the fan. The module 30includes a control 36 that allows a user to set the temperaturethreshold for allowing the fan to be activated. The module 30 alsoincludes a control 34 that allows a user to set the operating timeperiod for the fan 20 after the temperature falls below the threshold.

The bathroom 10 includes a shower/bath tub stall 40 having a shower pipe42 that terminates in a shower head 44 and having a bathtub spigot 46.Mounted on the shower pipe 42 is a smart sensor 50 that detects thetemperature increase in the shower pipe 42 when the hot-water valve isopened. Alternatively, the smart sensor 50 could be clipped onto thebathtub spigot 43. When a temperature increase is sensed by the sensor50, the sensor 50 communicates wirelessly with the module 30, whichsends a signal to the fan 20 turning the fan 20 on for theuser-selectable time interval selected with dial 34. In one form, thesensor 50 communicates wirelessly with the module 30 by way of an radiofrequency transmitter and receiver.

Batteries in the smart sensor 50 can be quite small, yet would beexpected to last at least 6 months, because a microcontroller in thesensor 50 would be asleep >99% of the time. It would wake up just onceor twice per minute to sense the temperature of the shower pipe 42. AnIC such as National Semiconductor's LM35 would be one suitabletemperature-sensing component of the sensor 50. A thermo-mechanicalswitch (e.g., bimetallic spring) could be used to activate thecircuitry, as an alternative to using the microcontroller's internalwatchdog timer.

Thus, the invention provides an automatic energy-efficient controllerfor a room exhaust fan. Advantageously, the user does not have toremember to turn on a bathroom exhaust fan because of the automaticoperation of the controller.

While in one example form the invention is an automatic control systemfor an exhaust fan of a room having a water dispensing conduit, theinvention is suitable for controlling any electrical device in a roomhaving a water dispensing conduit. For example, the invention couldcontrol operation of an electric towel warmer or a lighting system or anelectrically controlled fragrance dispenser. Also, another electricaldevice that could be controlled is a ventilation blower for a showerenclosure. It would turn on a few minutes after the shower has ended,and stay on for a programmed time interval, in order to dry off theshower walls and thereby to prevent the growth of mold and mildew. Sucha blower system can force air through a 3-inch duct located in a rearbottom corner of the shower, so that the air will circulate in a vortexand exit over the top of the shower door.

Thus, although the present invention has been described in detail withreference to certain embodiments, one skilled in the art will appreciatethat the present invention can be practiced by other than the describedembodiments, which have been presented for purposes of illustration andnot of limitation. Therefore, the scope of the appended claims shouldnot be limited to the description of the embodiments contained herein.

1. An automatic control system for an exhaust fan of a room having awater dispensing conduit, the system comprising: a control module thatcontrols delivery of electricity to the exhaust fan to activate anddeactivate the exhaust fan; and a sensor suitable for mounting on thewater dispensing conduit, the sensor sensing temperature of the waterdispensing conduit, the sensor transmitting a control signal to thecontrol module when a temperature above a predetermined temperaturevalue is reached on the water dispensing conduit, wherein upon receiptof the control signal, the control module activates the exhaust fan. 2.The system of claim 1 wherein: the control module activates the exhaustfan by providing electricity to the fan.
 3. The system of claim 2wherein: the control module includes a timer circuit that provideselectricity to the fan for a predetermined time period after which thefan is deactivated.
 4. The system of claim 3 wherein: the predeterminedtime period is a variable time period selectable by a user.
 5. Thesystem of claim 2 wherein: the control module includes a timer circuitthat provides electricity to the fan for a predetermined time periodafter temperature falls below the predetermined temperature value. 6.The system of claim 5 wherein: the predetermined time period is avariable time period selectable by a user.
 7. The system of claim 1wherein: the control module includes a control for setting thepredetermined temperature value.
 8. The system of claim 1 wherein: thewater dispensing conduit is a shower pipe.
 9. The system of claim 1wherein: the water dispensing conduit is a bathtub spigot.
 10. Thesystem of claim 1 wherein: the control signal is a radio frequencysignal.
 11. An automatic control system for an electrical device in aroom having a water dispensing conduit, the system comprising: a controlmodule that controls delivery of electricity to the electrical device toactivate and deactivate the electrical device; and a sensor suitable formounting on the water dispensing conduit, the sensor sensing temperatureof the water dispensing conduit, the sensor transmitting a controlsignal to the control module when a temperature above a predeterminedtemperature value is reached on the water dispensing conduit, whereinupon receipt of the control signal, the control module activates theelectrical device.
 12. The system of claim 11 wherein: the controlmodule activates the electrical device by providing electricity to theelectrical device.
 13. The system of claim 12 wherein: the controlmodule includes a timer circuit that provides electricity to theelectrical device for a predetermined time period after which theelectrical device is deactivated.
 14. The system of claim 13 wherein:the predetermined time period is a variable time period selectable by auser.
 15. The system of claim 12 wherein: the control module includes atimer circuit that provides electricity to the electrical device for apredetermined time period after temperature falls below thepredetermined temperature value.
 16. The system of claim 15 wherein: thepredetermined time period is a variable time period selectable by auser.
 17. The system of claim 11 wherein: the control module includes acontrol for setting the predetermined temperature value.
 18. The systemof claim 11 wherein: the water dispensing conduit is a shower pipe. 19.The system of claim 11 wherein: the water dispensing conduit is abathtub spigot.
 20. The system of claim 11 wherein: the electricaldevice is a blower.